The prior art includes support helices formed by a tube grooved in a helical line as disclosed in U.S. Pat. No. 3,515,798. However, it is difficult in manufacturing such a support helix to make a groove that will allow the helix to be pulled apart easily while maintaining sufficient strength to hold the helix together and support the resilient compression of the expanded resilient sleeve.
To overcome the above noted problem, the support helix of U.S. Pat. No. 4,389,440 is wound from a ribbon, and the connection areas are produced by welding or tacking. This is, however, an expensive process for making the helix. Another solution, disclosed in U.S. Pat. No. 4,503,105, is to make the tubular base body with a constant wall thickness, to include circumferentially spaced longitudinal ribs on the inside wall of the body and to cut through the constant wall thickness in a helical pattern leaving the spaced ribs to hold the helix together. This requires more material in the support helix and a larger diameter support helix for a specified internal clearance for the cable or other article to which the resilient sleeve is to be applied.
The objective is, of course, to make the support helix of an inexpensive material and to produce it inexpensively with as high as possible a strength against the compression force exerted by the sleeve while at the same time producing a helix that will unwind with as small a force as possible.